1. Field of the Invention
The present invention relates to a printed circuit board and a method of manufacturing the printed circuit board.
2. Description of the Related Art
Recently, demands for a technology which directly mounts a semiconductor chip on a printed circuit board has been increasing in response to the development of highly-densified semiconductor chips and the high-speed transmission of signals. Consequently, the development of printed circuit boards of a high density and high reliability which are suitable to highly-densified semiconductor chips is required.
Requirements for a printed circuit board of a high density and reliability are closely related to the specifications of the desired semiconductor chip. The printed circuit board having high density and high reliability must further be developed to have many characteristics such as the implementation of fine circuits, excellent electrical properties, structure for high-speed transmission of signals, high reliability, high performance, slimness and the like. Accordingly, a technology for printed circuit board which is capable of forming fine circuit patterns and micro via-holes is required in order to meet these needs.
FIGS. 1 to 5 are cross-sectional views showing a conventional process of manufacturing a printed circuit board. The conventional process of manufacturing a printed circuit board will now be described with reference to the drawings.
First, as shown in FIG. 1, a copper clad laminate which comprises an insulating layer 12 and copper layers 14 disposed on the insulating layer 12 is prepared.
As shown in FIG. 2, a via-hole 16 for the interlayer electrical connection is formed in the copper clad laminate using mechanical drilling or laser machining.
As shown in FIG. 3, a plated layer 18 is applied on the inner wall of the via-hole 16 as well as the copper layer 14. In this regard, the plated layer 18 includes an electroless plated layer formed by an electroless plating process and an electrolytic plated layer formed by an electrolytic plating process. For the convenience of explanation, the plated layer 18 is shown in FIG. 3 as being composed of a single plated layer.
As shown in FIG. 4, the copper layer 14 and the plated layer 18 are patterned to create a circuit layer 20.
Finally, as shown in FIG. 5, a solder resist layer 22 having an opening 24 through which a pad part of the circuit layer 20 is exposed is disposed on the insulating layer 12, thus finishing a printed circuit board 50.
The printed circuit board which is manufactured through the conventional process is configured such that the circuit layer 20 including the pad part is formed on the insulating layer 12 and the solder resist layer 22 for protecting the outermost circuit layer 20 is formed on the insulating layer 12. Consequently, the printed circuit board 50 configured in this manner is problematic in that its thickness is increased and reliability of the high density circuit is deteriorated.
Furthermore, since the printed circuit board is configured such that the pad part and the solder resist layer 50 are formed on the insulating layer 12, stepped portions occur in the course of machining the openings 24 through which the pad part is exposed, thus making printability of external connection terminals uneven. In addition, since the openings must be machined while taking into consideration manufacturing error, the openings 24 are inevitably made larger than the pad part, thus reducing a degree of freedom in the design of the openings 24.